1. Field of the Invention
The present invention relates to package structures and fabrication methods thereof, and more particularly, to a package on package (POP) structure and a fabrication method thereof.
2. Description of Related Art
As electronic products are developed towards miniaturization, printed circuit boards have less area available for disposing semiconductor packages. Therefore, semiconductor packages are vertically stacked to form package on package (POP) structures to meet the demands for small surface bonding area and high component density.
FIG. 1 is a schematic cross-sectional view of a conventional POP structure.
Referring to FIG. 1, two packages 11, 12 are provided. An encapsulant 111 is formed on the package 11 and then a laser ablation process is performed to form a plurality of openings 1110 in the encapsulant 111 for exposing conductive pads 112 of the package 11. Thereafter, a plurality of conductive elements 113 are formed on the conductive pads 112 in the openings 1110. Further, a plurality of solder balls 121 are formed on a lower surface of the package 12. Then, the package 12 is stacked on the package 11 and electrically connected to the conductive elements 113 of the package 11 through the solder balls 121, thereby forming a POP structure.
However, to form the openings in the encapsulant, a large laser drilling depth is required, thus increasing the fabrication time and reducing the production efficiency. Further, as I/O counts increase and the distance between the conductive pads decreases, solder bridging easily occurs during stacking of the packages, thereby reducing the product yield.
Therefore, there is a need to provide a POP structure and a fabrication method thereof so as to overcome the above-described drawbacks.